Archive for the 'Fukushima Reactor Accident' Category

… it’s important that everyone realize what I have already said concerning this set of accidents. The main stream media (both print and television) continue to point towards avoiding a core melt event, as if it will announce itself with some sort of trumpet blast and melt through the earth. As I have explained, it doesn’t happen that way. The corium, if it makes it through the lower reactor vessel head, will disperse and cool from that dispersal, not even making it through the lower basemat of concrete.

The cores for Units 1, 2 and 3 are already damaged. They are partially melted, and partially shattered and rubblized, sitting in the lower part of the reactor vessel. Most of the radiological source term that can be expected to be released from the core to containment has already been released. It is being held up inside hard containments and depleted via radioactive decay, plateout, etc.

The work now has to do with mitigation of the radiological source terms, from water injection into the reactor coolant system, water washdown of plant components, and so on. If the semi-volatile fission products and alkali metals are in effluent, they will likely not re-evolve to the atmosphere in large quantities. Most importantly, for now, the Spent Fuel Pools deserve attention, and hopefully the operators will be able to mitigate zirconium fire events in the pools.

Nature has also learned that initial CTBTO data suggest that a large meltdown at the Fukushima power plant has not yet occurred, although that assessment may change as more data flow in during the coming days. Lars-Erik De Geer, research director of the Swedish Defence Research Institute in Stockholm, which has access to the CTBTO data and uses it to provide the foreign ministry and other Swedish government departments with analyses, says that the data show high amounts of volatile radioactive isotopes, such as iodine and caesium, as well the noble gas xenon. But so far, the data show no high levels of the less volatile elements such as zirconium and barium that would signal that a large meltdown had taken place — elements that were released during the 1986 reactor explosion in Chernobyl in the Ukraine.

And today the AP acknowledges that the cores in Units 1, 2 and 3 are “partially melted.” The Captain’s Journal is a week or so ahead of the rest of the nuclear experts.

Japanese authorities have taken a major step in managing a nuclear crisis by connecting all six earthquake-damaged reactors to power supply, but it’s too soon to say the crisis has reached a turning point, experts said on Monday.

Power has been connected but not switched on to crank up most coolers and pumps, which may have been badly damaged in the quake and tsunami that on March 11 triggered the world’s worst nuclear accident since Chernobyl. Only one pump has been activated.

The damaged reactors and their spent fuel pools at the Fukushima Daiichi nuclear power plant, 240 km (150 miles) north of Tokyo, urgently need cooling from air-conditioners and from water pumped in.

U.S. Energy Secretary Steven Chu, asked by CNN whether the worst of Japan’s 10-day nuclear crisis was over, said: “Well, we believe so, but I don’t want to make a blanket statement.”

U.S. Nuclear Regulatory Commission Chairman Gregory Jaczko added that radiation levels at the plant appeared to be falling.

But nuclear experts in the United States and elsewhere were not quite as positive.

“I am not sure if the crisis has passed but it is definitely a step in the right direction,” said Peter Hosemann, a professor at the University of California Berkeley’s Nuclear Engineering Department.

“It is getting better. However, we don’t know if the pipes and connections and pumps still work at this point or what works and what not. But having power makes external water supply easier.”

This is a positive step. This is good. This makes addressing the problems an order of magnitude easier. But don’t hurry to a conclusion. Water may have intruded into terminal cabinets, circuitry, pump motors, transformers, load centers and motor control centers, and getting power to the plant is not the same thing as getting power to individual components. There will be ground faults, broken connections, flooded components, and breakers that trip open on over-current and under-voltage when they are closed. It will be a massive headache for the operators.

This isn’t over. The Japanese are performing heroically as I have observed. They are improving the situation. But habitability of land, edibility of crops, cleanup of the plant, and recovery operations for the rubblized reactor cores will take time and money. Pray for the Japanese – and don’t jump to any conclusions from MSM reports, like the notion that the fact that Unit 3 contains mixed oxide fuel (MOX) makes it somehow more dangerous than UO2 cores. Please don’t fall for the hype. Fuel fines will not become aerosolized or airborne, and the Plutonium is part of a metal crystalline structure. It will stay bound within the fuel matrix.

For comparison, a human receives 2,400 micro sievert per year from Natural radiation in the form of sunlight, radon, and other sources. One Chest CT scan generates 6900 micro sievert per scan.

Fukushima Daiichi Unit 1 reactor

Since 10:30AM on March 14, the pressure within the primary containment vessel cannot be measured.

At 12:50PM on March 17, pressure inside the reactor core: 0.185MPa.

meters below the top of the fuel rods.At 12:50PM on March 17, water level inside the reactor core: 1.

Fukushima Daiichi Unit 2 reactor

At 12:25PM on March 16, pressure inside the primary containment vessel: 0.40MPaabs.

At 12:50PM on March 17, pressure inside the reactor core: -0.027MPa.

At 12:50PM on March 17, water level inside the reactor core: 1.8 meters below the top of the fuel rods.

Fukushima Daiichi Unit 3 reactor

At 12:40PM on March 16, pressure inside the primary containment vessel: 0.23MPaabs.

At 6:15AM on March 17, pressure inside the suppression chamber was observed to fluctuate.

At 7:00AM on March 17, pressure inside the suppression chamber: 0.22MPa.

At 7:05AM on March 17, pressure inside the suppression chamber: 0.44MPa.

At 7:10AM on March 17, pressure inside the suppression chamber: 0.26MPa.

At 7:15AM on March 17, pressure inside the suppression chamber: 0.52MPa.

At 7:20AM on March 17, pressure inside the suppression chamber: 0.13MPa.

At 7:25AM on March 17, pressure inside the suppression chamber: 0.57MPa.

At 9:48AM on March 17, a Self Defense Forces helicopter made four water drops aimed for the spent fuel pool.

At 4:35PM on March 17, pressure inside the reactor core: 0.005MPa.

At 4:35PM on March 17, water level inside the reactor core: 1.95 meters below the top of the fuel rods.

At 7:05PM on March 17, a police water cannon began to shoot water aimed at the spent fuel pool until 7:22PM.

At 7:35PM on March 17, five Self Defense Forces emergency fire vehicles shot water aimed at the spent fuel pool, until 8:09PM.

Fukushima Daiichi Unit 5 reactor

At 2:00PM on March 16, the temperature of the spent fuel pool was measured at 145 degrees Fahrenheit.

Fukushima Daiichi Unit 6 reactor

At 2:00PM on March 16, the temperature of the spent fuel pool was measured at 140 degrees Fahrenheit.

Notice the pressure inside the Unit 1 reactor vessel: 0.185 MPa, which is 26.834 psi. Units 2 and 3 are lower, essentially atmospheric pressure, and Unit 4 isn’t even included in the report. The NRC has some hypothetical dose projections (that are in my opinion far too high, and I don’t believe them), but it isn’t difficult to see why the NRC has recommended evacuation for U.S. citizens.

Help is on the way, and they hope to install and align emergency power soon. It wasn’t long after the tsunami that they had portable emergency diesel generators delivered, but the tsunami had cleared out all offsite power, including stepup transformers and connections. They literally had nothing to which to connect (that could be readily ascertained as the power source for any specific component). It was a jungle of cables.

But it’s important that everyone realize what I have already said concerning this set of accidents. The main stream media (both print and television) continue to point towards avoiding a core melt event, as if it will announce itself with some sort of trumpet blast and melt through the earth. As I have explained, it doesn’t happen that way. The corium, if it makes it through the lower reactor vessel head, will disperse and cool from that dispersal, not even making it through the lower basemat of concrete.

The cores for Units 1, 2 and 3 are already damaged. They are partially melted, and partially shattered and rubblized, sitting in the lower part of the reactor vessel. Most of the radiological source term that can be expected to be released from the core to containment has already been released. It is being held up inside hard containments and depleted via radioactive decay, plateout, etc.

The work now has to do with mitigation of the radiological source terms, from water injection into the reactor coolant system, water washdown of plant components, and so on. If the semi-volatile fission products and alkali metals are in effluent, they will likely not re-evolve to the atmosphere in large quantities. Most importantly, for now, the Spent Fuel Pools deserve attention, and hopefully the operators will be able to mitigate zirconium fire events in the pools.

The Japanese are performing heroically, and the main stream media will catch up in several days (or weeks). The current efforts are focused on radiological source term and thus dose mitigation, not the prevention of core melt events.

Today for the first time the NRC went on record saying that the Fukushima Unit 4 Spent Fuel Pool was in deep trouble.

Mr Jaczko, who was briefing US politicians in Washington, said the NRC believed “there has been a hydrogen explosion in this unit due to an uncovering of the fuel in the spent fuel pool”.

“We believe that secondary containment has been destroyed and there is no water in the spent fuel pool. And we believe that radiation levels are extremely high, which could possibly impact the ability to take corrective measures.”

There has been some disputing going on between Japanese officials and the NRC, but apparently not enough to cloud the trouble, and the apparent plans to address it.

As U.S. and Japanese officials disagreed on how to characterize the seriousness of the nuclear crisis, police planned to use a water cannon truck — normally used for crowd control — to try to cool an overheated and possibly dry spent-fuel pool, one of an escalating series of malfunctions at the Daiichi plant in Fukushima prefecture, 150 miles north of Tokyo. Without cooling, the spent rods could emit radioactive material.

[ … ]

In Washington, U.S. Nuclear Regulatory Commission Chairman Gregory Jaczko said at a congressional hearing that all the water has evaporated from the spent fuel storage pool at the complex’s No. 4 reactor. Japanese officials have not confirmed that.

While not acknowledging that the Unit 4 SFP is a problem, they acknowledge plans to use a water cannon to get water into the pool.

As I said before boiloff, dryout and zirconium fires in the SFP pose a more significant risk than what is happening inside a hard containment.

Japan suspended operations to prevent the stricken Fukushima Dai-ichi nuclear plant from melting down Wednesday after a surge in radiation made it too dangerous for workers to remain at the facility.

Chief Cabinet Secretary Yukio Edano said work on dousing reactors with water was disrupted by the need to withdraw.

Foxnews is so far the only news media outlet reporting this. Thus far I have made my objections known to the paucity of good information coming from Japan, and the misinterpretation and mischaracterization of the little that is available by MSM outlets. It isn’t clear what this means. It could mean that that efforts to ensure core cooling are being abandoned, and this is bad, but not the same thing as abandoning the plant entirely. In the former case, we still have cores that have been partially rubblized and melted, fission products released, and partially contained within a hard containment, but attention still being paid to maintaining the integrity of the spent fuel pools. In the later case, this is very bad indeed. I had said earlier that I was actually more concerned about the radiological source term in the spent fuel pool than I was over the cores and containment.

This goes to show just how bad the situation is – no, not the situation with the reactors (which is bad enough), but the situation with the flow of good information.

It had previously been reported that there was a fire in the Spent Fuel Pool of the Unit 4 nuclear reactor. However, it wasn’t quite what it seemed.

Tokyo Electric Power Co. said that an oil leak in a cooling water pump at Unit 4 was the cause of a fire that burned for approximately 140 minutes. The fire was not in the spent fuel pool, as reported by several media outlets. Unit 4 was in a 105 – day – long maintenance outage at the time of the earthquake and there is no fuel in the reactor.

Near the plant entrance, which is somewhat removed from the building, radiation rose to 11.93 millisieverts per hour at 9 a.m. but was back down to 0.5964 millisieverts at 3:30 p.m.

Elevated radiation levels were also detected in northern Kanto and the greater Tokyo area, which is further south. Readings from 9 a.m. to 5 p.m. averaged 10 times higher than normal in some places, but still far below any level that would have an effect on the human body.

The No. 4 reactor had been shut down for a routine inspection, but the water temperature in the pool used to store spent fuel rods was rising. With the power now out and crews unable to enter the building, there is no way to know what is happening in the pool. If the temperature continues to rise, the rods could melt, threatening to release huge amounts of radioactive material.

From having performed the spent fuel characterization and shielding calculations, I know that the dose rate in a fuel pool building with the fuel uncovered by water would be as high as 50,000 rads/hr or even higher depending upon specific assumptions such as fuel burnup, decay time, enrichment, etc. That’s why most U.S. reactors have multiple (not just redundant, but multiple) means of makeup of borated water to the Spent Fuel Pool.

So the operators cannot get into the building to observe the conditions due to lack of habitability. If this fire is consuming oil, that’s one thing. If there is a Zirconium (cladding) fire due to loss of water over the fuel assemblies, then given the lack of a hard containment for the spent fuel building, I am actually more concerned about that than releases of radioactivity from the reactor buildings due to holdup, decay, sedimentation and plateout of fission products inside containment.

But the point is that there is still a dearth of good, high quality, technical information flowing our direction. Foxnews reported this morning that the dose (rate – although they didn’t understand that dose [rate] has units of time and didn’t report it as such) from radiation from the plant was the same immediately surrounding the plant and at 18 miles from the plant. Of course, this is physically impossible given that radiation decreases like sound and light with the inverse of the square of the distance from the source (1/R²).

There is a dearth of quality, technically correct information and commentary on the Japanese reactor accidents occurring at the Fukushima nuclear power plant. In fact, some of it is downright wrong. There is no hope of comprehensively reproducing a time line or of surveying all of the available news releases or reports. I’ll link some very good sites shortly that will assist you in studying the future commentaries and reports. Just to set the tone, if you are interested in one-and-a-half minute reading and tabloid hysteria, close this web page now. Go to the tabloids – or most MSM sites – or so-called news television (with their “nuclear expert” du jour). I won’t purvey hysteria or ignorant analysis. I’ll begin with things that can’t happen, and phrases and terms to avoid in your reading and viewing. We’ll move to a quick summary of what we know thus far about the accident(s), and close with an assessment of the consequences of this reactor accident for the future of Japan.

Perhaps the worst tabloid journalism thus far has come from Geraldo Rivera on Foxnews on Sunday evening. Thousands of souls had been swept into the sea, and Geraldo was discussing how “radiation was like that voodoo stuff – you can’t see it, and that’s what makes it scary!” The kind of hysteria extends to supposedly smart people like Charles Krauthammer, who said:

It’s a terrible potential. If you get a meltdown, of course, there is a catastrophe for the region. But also every 20 years we say let’s try again with nuclear energy, it’s clean energy — it doesn’t put stuff into the atmosphere. [Now] if you get a “China Syndrome” as in 1979 … it could put the nuclear [industry] out of business for decades.

The Daily Mail reports that “As fuel rods melt, they form an extremely hot molten pool at the bottom of the reactor that can melt through even the toughest of containment barriers.” To dispense with the myths, the China Syndrome was a movie. What happens in the analytical models, and also in actual reactor accidents like Three Mile Island (TMI) Unit 2, is that the corium, that mixture of melted fuel, cladding and other internal reactor components like control rods and guide tubes, forms in some of the channels, further blocking fluid flow. Eventually in an extreme reactor accident, much of the fuel shatters and becomes rubblized in the lower reactor vessel head. This is in fact what happened at TMI in large measure, along with some core melting.

It doesn’t require melted fuel to release fission products. Having written computer codes that model such releases, I can observe that much of the fission products are released in fuel heatup, and most releases occur prior to achieving fuel melt temperature, including most or all of the Noble Gases (Kr, Xe), much of the semi-volatiles (halogens) and some of the alkali metals (e.g., cesium). Don’t forget this point. This is important and I’ll come back to this later.

The corium isn’t modeled to melt through the lower vessel head except in the worst accidents where there is no coolant at all. This isn’t the case for the Fukushima reactors. Even in the event of complete breach of the lower vessel head, the corium doesn’t under any circumstances achieve melt-through of the lower basemat, which in some U.S. reactors is as much as 12 feet of concrete. The corium disperses and cools from the dispersal. There is no such thing as the China syndrome. That’s just a dumb ass movie. And reactors also don’t explode like nuclear weapons. Nuclear radiation isn’t voodoo, and we know how to achieve protection against it.

Now to what we know about the accident. When the tsunami occurred it disabled the offsite power to the plant. Emergency diesel generators automatically started, and they functioned for approximately one hour until they shut down due to tsunami-induced damage to their fuel supply. Power to the control valves in the reactor makeup operated until they lost battery backup. DC power from batteries was consumed after about eight hours of operation. The plant sustained a complete blackout (loss of all power), and it was at this point that fuel damage and Zirconium alloy (Zircalloy) – water interactions occurred, i.e., cladding oxidation. This is an exothermic reaction and produced more heat, adding to the fuel fission product decay (or residual) heat to be removed by the cooling system. It also produces hydrogen.

During some point in the past several days, hydrogen explosions occurred on Unit 1. In an attempt to prevent the hydrogen concentration from being above the explosive limit, releases were made from Unit 3. Ironically, it was likely a valve opening or some other electrical arc that caused the hydrogen explosion that occurred on Unit 3, further damaging not only Unit 3 but apparently also parts of Unit 2. Any hydrogen explosion that looks like this has already degraded a lot of nuclear fuel.

In spite of Russian experts who wax eloquent about how the world learned from the Chernobyl accident and how we’re better able to handle reactor accidents because of the Russian experience, the Japanese reactor accidents aren’t like Chernobyl, and it isn’t because we learned from the Russian design. I studied thousands of documents concerning Chernobyl and performed many calculations. I trained the DOE safety analysis engineers on the nuclear design characteristics of the RBMK-1000 reactor (not as a DOE employee).

The RBMK reactor design was loosely neutronically coupled, and had an overall positive power coefficient. That is, it was graphite-moderated, and since the water was a neutron poison rather than the moderator, the reactor was “over-moderated.” This means that upon a loss of coolant, the reactor experienced a power excursion. It had a positive void coefficient, leading to an increase in reactor power by a factor of 100 in less than 1 second. Furthermore, its containment structure was little more than a sheet metal “Butler Building.” The core was in flames and pouring fission products into the atmosphere. More than 30 souls perished attempting to mitigate the accident, and many more contracted cancer from the releases of radioactivity.

Despite what some of the more “conservative,” pro-nuclear “experts” have said on national TV, the Chernobyl accident was a catastrophe. I was in training with an engineer from Kiev not too many years ago, and he informed me that residents of Kiev still have to frisk their food with a GM detector and pancake probe prior to eating to ensure that they aren’t ingesting radioactivity.

So why was the RBMK reactor designed this way? For the production of weapons-grade fissile material. I have pictures of the Russians performing online refueling operations at the Chernobyl site to remove the weapons material. The Russians tried to combine commercial nuclear power with weapons production. The RBMK design is the result. U.S. reactors are designed by federal code with a negative overall power coefficient (GDC 11), which shuts the reactor down in a loss of coolant or fuel heatup.

The Fukushima reactor accidents aren’t Chernobyl because they have a hard containment design and a negative power coefficient like U.S. reactors. Unfortunately, that containment design is being breached periodically to release steam from the sea water that is flooding the core, and with the steam releases come radioactivity releases. As I said before, much of the release of fission products to the containment has likely already occurred (meaning that while it’s important to cool the core, its also the case that sedimentation, washout, plateout and other removal mechanisms are acting on the fission products (including radioactive decay).

We in the U.S. had our core melt event; it was TMI. There were essentially no releases of radioactivity and thus no health affects due to the hard containment design. The Fukushima reactor accidents are worse than TMI given the breach of containment, but with the evacuation that has already occurred, the health affects will be minimized.

The main cost now to TEPCO will be the cleanup and decommissioning of the damaged reactors, which likely have rubblized cores sitting in the reactor vessel. It will take a decade and tens of billions of dollars. Just as with the Takaimura criticality accident, we will probably see senior company officers bowing before the nation and asking forgiveness. This will probably spell the end of many careers, and the beginning of much soul searching over design and licensing basis seismic events, flood events and related design criteria.

There are many reports that have incorrect or incomplete information. The reports on exposure to the 7th fleet is remarkable for its lack of technical detail. We could perform a dose reconstitution with the available data, but we aren’t given any. There are incorrect and inconsistent units of radiation being reported, and there are technical facts gotten wrong. It’s best not to speculate on what we don’t know, and it’s best not to listen to the “experts” on television.

This is a serious reactor accident, one for the books. Nuclear engineers will be studying this accident for decades to come, and it will affect reactor regulation in both Japan and the U.S. But the Japanese worked remarkably efficiently to evacuate residents, and thus radiation exposure will be minimized. This was yeoman’s work given the state of transportation after the tsunami. The Japanese faced the perfect storm of problems, and they performed admirably.

But what this accident should not do is cause us to jettison the promising future of nuclear power because there might be some cesium uptake in Tuna in the Pacific. When nuclear workers receive regular body burden analysis to assess the radioactive content in their body, the technician can tell if they are hunters. “Do you hunt, sir? Yes, I hunt deer. Oh, that explains the Cs-137 spike I see.” The Cs-137 doesn’t come from commercial nuclear reactors. It comes from fallout from nuclear weapons testing during the 1950s and 1960s. We’ve been there and done that. It’s not a problem.

Only tabloid media could take a situation where thousands of souls were swept away in a tsunami and ignore that story for the real drama of a melted core (in which one soul has perished, and that from an industrial accident). We need to maintain our perspective, and the proper perspective isn’t to have nightmares of melt-throughs to China. We should leave that to the purveyors of hysteria.

Some good links (I will add to these later):

ANS Nuclear Cafe (for the best coverage and analysis of the Fukushima reactor accidents)

NUREG-1250, “Report on the Accident at the Chernobyl Nuclear Power Station.”